1. Field of the Invention
The invention relates to a signal amplifying circuit, and more particularly to an audio signal amplifying circuit which is used to prevent POP noises from occurring in an audio amplifier.
2. Description of the Related Art
Audio amplifiers are widely used in multimedia electronic products, which amplify an audio input signal and generate an output current or voltage according to the amplified audio signal to drive a speaker for generating sound. In general, a loading of the speaker is small. Thus, larger output voltages or current provided by an audio amplifier is needed to drive the speaker.
When an audio power amplifier is powered on or off, an uncomfortable pop noise may be induced if the switching is not smooth enough during the period when an audio signal suddenly appears or disappears. For example, if the audio amplifier is enabled or disabled at the moment that the voltage of the audio input signal is at a maximum value or a minimum value, a large output signal is generated instantaneously, and then an annoying pop noise is generated through the speaker.
Therefore, control circuits and control methods thereof are desired to avoid generation of POP noises for an audio amplifier.